RE: Best Practice - beyond schema
The problem of a schema that matches multiple customers with different requirements is to establish authoritative controls. Multiple authorities are in effect. The single schema approach with multiple optional elements can govern but is too weak to be said to govern transparently. The problem of multiple schemas is that the control is referential beyond the fact of the specific schema used for the local or specific transaction, so not unified and proof must always be offered that the schema-of-use is in fact, mapped correctly to the local rules of the process. This means transparency is lost. If the authorities are local, the schema from which the schema-of-use is derived is the governing schema and the authority of reference has little value beyond being a library registry. An alternative is to move the local definition to a transformation document, eg, XSLT over the XML Schema. The technical advantage here is to have the modifications in a single automated document including any value constraint controls which presumably will be local The XML Schema is one and the authority is centralized. The XSLT modifier is one and is owned by the local authority. Given the nature of electoral processes, the ability to vette the controls and cite them as singletons (one XML Schema, one XSLT per local definition) would seem to be important to the transparency of the process. len -----Original Message----- From: Paul Spencer [mailto:paul@a...] There are two reasons for needing to go beyond XML Schema on a project that is using XML Schema as its base constraint syntax. The first is where XML Schema cannot express the constraints required, for example, a section of a message that is required if the value of a previous element is "yes", but not if it is "no". Languages such as Schematron go some way to address this and can be used either embedded in an XML Schema schema or as free-standing documents. I will shortly be making recommendations in this area to the UK Govt, and would welcome a discussion here at some point.
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